There are some key differences and drivers this year, compared to years past. Several of these have only recently become apparent, while a few were known prior to the start of the Pacific & Atlantic Hurricane Seasons.

Firstly, this entry is not looking solely at the Atlantic. And when considering potential U.S. impacts, some seasons just have the ability to challenge the imagination, and almost defy logic. It starts to become necessary to either reach way back into long-forgotten historical records, or contemplate the possibility that a new record may get set. 2015 could be shaping up to be just such a year.

With deference to the title, it is informative to look at the 2014 season in both the Atlantic & Pacific. Prior to the start of each, it was widely expected to be average to below average in the Atlantic, and slightly to moderately above average in the Pacific, as an El Niño was expected to slowly develop and be fully in effect by the winter of that year. That never happened. Waters in the Niño 3.4 region trended back to neutral (3MMAs ASO 0.2, SON 0.4, OND 0.6, NDJ 0.6, DJF 0.5, JFM 0.4). "Warm" Niño 3.4 region (i.e., 5oN-5oS, 120o-170oW) events are defined as 5 consecutive overlapping 3-month periods at or above the +0.5 anomaly.

However, throughout the year evidence began building that the AMO (Atlantic Multidecadal Oscillation) may have started trending negative (cool) for the first time in 20 years, and now many specialists believe this is indeed underway. If correct, the multidecade era of generally more active Atlantic hurricane seasons/less active Central-Eastern Pacific hurricane seasons may already be closing.

Also during the 2014 hurricane seasons, the wave train off of Africa was really subdued - the Saharan Air Layer (SAL) just drying out and polluting the entire stretch from east Africa well across the Atlantic. Hazy days with tan to reddish sunsets became frequent all the way to gulf states like Florida and Texas. Long bouts of high windshear and sinking, dry air effectively put the lid on most of the (relatively few) features that had a snowball's chance to form.

The 2014 Atlantic Hurricane Season ended with the fewest named storms since 1997, despite the fact that the much advertised El Niño never arrived.

So what's so different in 2015?

Well for starters, we look to be in the early to middle phase of a strong to very strong El Niño. For certain this time. In fact, indications are that this could rival our biggest El Niños of the past, and maybe even surpass them.

Another, it still looks as if that at the very least there could be a temporary pause - if not an absolute switch - from the positive phase of the AMO (warmer Atlantic), to the negative (cooler Atlantic).

Another, the trend of globally higher average SSTs (Sea Surface Temperatures) continues - something that has increasingly been expanding the tropics poleward - at a rate of about 0.7 degrees latitude per decade - and so often helping set the plate for conditions more favorable for subtropical and tropical cyclone development and sustainability at increasingly higher latitudes.

Interestingly, the SAL is still really abundant in 2015, but disturbances across Africa have just blossomed of late (Image below)

These thunderstorm complexes sometimes sustain as waves when they roll into the Atlantic, where they either die (over water or land), develop, or end up in the Pacific. The sheer numbers of them being created now is raising eyebrows - and not just for the Atlantic - because we are in a year when conditions are so favorable in the central and eastern Pacific, and waters so anomalously warm, that U.S. states and territories and vacation spots not accustomed to having to deal with tropical cyclones are definitely at greater risk.

So what all possibilities might we be wise to consider in such an unusual year?

* There is actually a chance that the Atlantic could end up with an average to even above average number of named storms and/or hurricanes, after all - and this is very reliably backed up in the historic record. 1972, which saw the third strongest El Niño in the most data rich period (since 1950), actually ended up with 19 Tropical Cyclones in the Atlantic basin.

* Like 2014, the Hawaiian archipelago is clearly at great risk - and possibly even more so than in 2014, when we saw the strongest tropical cyclone on record to make landfall on the Big Island, Iselle, wreak havoc there. Iselle, which made landfall as a powerful 60MPH tropical storm, was at its peak a 140MPH Category 4 hurricane prior to weakening on approach from the southeast. Winds gusted to to 72 mph at the Oahu Forest, and 91 mph on Mauna Kea. Parts of the Big Island picked up over a foot of rain, and flooding was widespread.

* Unlike 2014, the Hawaiian islands will see more approaches from the south, which lends to tropical cyclones traveling over much warmer waters and through more unstable air prior to crossing the latitudes of the islands. The most extreme example of this in recent recorded history is Hurricane Iniki (1992). Thousands of homes were destroyed and there were at least six confirmed deaths.

* Remembering 1992, it also makes one think about teleconnections. And while history doesn't necessarily repeat itself exactly, it does rhyme. Also in 1992? An August Atlantic tropical cyclone named Andrew.

* Years with unusually warm eastern Pacific waters can also favor cyclones traveling north or recurving north-northeastward during the late summer to fall period, which can and has put the Southwest at risk. The most extreme example of this in reliably reconstructed history is The 1858 San Diego Hurricane (85MPH). More recent examples, in the satellite era, include 1997's Nora, which after making landfall in Baja California, tracked into California and Arizona as a bona fide mid-range tropical storm, with Yuma, Az. reporting maximum sustained winds of 57MPH and higher gusts. Nora's remnant circulation even sheared off the tops of hundreds of large trees in southwestern Utah.

CPC has come out today with their latest two week Global Tropical Hazards & Benefits forecast.

A Moderate risk of tropical cyclone development in the Atlantic is expected to continue for the next two weeks, with Moderate to High risk of further development in the east Pac towards Hawaii also expected to continue, and in fact, be on the increase out there, during Week 2.

It is noteworthy how relatively subdued they expect the west Pac to be during this period.

Another potential, if not likely driver of the 2015 Atlantic & Pacific Hurricane Seasons, happens to be a giant blob of highly anomalous warm waters off the west coast of North America. And yes, The Blob truly seems to be the nomenclature being used to address it, so there we have it. Run, don't walk.

The Blob itself is thought by some to possibly be a precursor to the outright flipping of the Atlantic Multidecadal Signal (AMO) to the Pacific Multidecadal Signal (PDO), but this is speculative, as the behavior and nature of both are still not all that well understood.

The Blob existed in the 2014 season, but the intensity has since increased and expanded, substantially. The Blob is thought to be a key ingredient in the ongoing heatwaves in the Pacific Northwest, and a key ingredient in forcing fronts unseasonably far south this summer over the eastern two-thirds of the country.

With the strong El Niño fueled tropical waters being both warmer and more poleward than in past seasons, we have recently seen a spate of tropical storms and hurricanes developing and intensifying in the central to eastern Pacific in locations not usually expected to see such activity.

With "Blob" waters off the California coast now running as much as ten plus degrees above normal (using this as a decent proxy for the far eastern Pacific), and many weeks in the Pacific Hurricane Season left to go, the period from the current month of August to at least late October may want to continue to surprise, even if all of the other factors listed in the Original Post above were not in play, but which they also happen to be.

Please keep in mind that the purpose of this Forum is really to discuss tropical cyclones that are active in other storm basins. Your questions are really off-topic for this Forum. I'd recommend using the PM feature to discuss your questions with the post originator.
ED

Two areas of subtropical or tropical nature to recently affect the Hawaiian islands, and two more that could be setting up to do so in the near future. The archipelago has been seeing far more than its usual share this year.

Above: Kilo finally pulled his weight - fortunately doing so while much farther west than initially forecast. And so, Kilo joins the ranks of two other Majors currently out in the GOES WEST view of the Central & Eastern Pacific. Ignacio (middle) and Jimena (right) have model support that suggest a risk to at least some of the Hawaiian islands, and a few runs even recurve Jimena, to send the cyclone, or its potent remnants, into the Pacific NW.

From left to right:
Kilo is now a powerful Typhoon in the W Pac. Ignacio has just been declared "Post-Tropical." A powerful Post-Tropical Cyclone, Ignacio is forecast to bring stormy conditions to British Columbia. Jimena is still an intense hurricane, and there is a chance it could bring the Hawaiian islands inclement weather next week. Kevin is stretching out/decoupling tonight over the Baja. Over the weekend Kevin's remnants will likely enhance monsoonal rains in the southwest, and even supply additional moisture all the way to Canada.

It is now certain that we are in the midst of a strong and record-setting El Niño. Also, as noted above in this thread, nearly the entire NEPAC is awash in highly anomalously warm waters, a stubborn feature that has been named The Blob.

While early on it was very clear that the dice were loaded for an El Niño, what was far less certain was should one develop, how strong it would become.

Other critical questions for answering the strength and frequency (or lack thereof) of systems which would form in both the Pacific & Atlantic were even less certain. Two of these were: How many seedlings/disturbances would there be for these exceptionally warm waters to cook, and: How might the massive Blob of very above average SSTs in the East Pac Subtropics affect things, if at all.

Now all three of these questions have largely been answered. 1) We are witnessing a historic El Niño 2) There have been a high number of seedlings in both ocean basins, and 3) The Blob has effectively helped amp up synoptic scale Trofs and Ridges around the country, and in part thereby increasing the likelihood of Trofs along the west coast being able to sweep up tropical cyclones, or at least their remnants and moisture, and tossing them across (anomalously warm waters) and into the desert southwest.

This pattern looks to stay in place throughout the remainder of this year, and likely into at least next spring, as well - alternating at least several more times between deflecting Ridges, and grabbing Trofs, as the atmosphere is highly amplified.

While a deflecting/redirecting Ridge might be welcomed by those from Oregon to Alaska, which would also like to see a hearty winter for a change, this looks less likely, as generally speaking, a strong El Niño ramps up the southern branch of the jet, and sends rounds of juiced-up extra-tropical/sub-tropical cyclones blazing across the southwest, extreme south, and southeast, sometimes producing record precipitation, that owing to its warm water connections, tends to fall mostly as rain, that just runs off - with often deadly repercussions.

It has been so long since much of the southwest has seen significant rain, that many who live there, and those who are visiting, may have almost no idea how quickly these torrents can become flash floods. Sadly, we saw this play out today in the Utah-Arizona border towns of Colorado City and Hildale, where at least a dozen people lost their lives - reportedly at least some of whom that had moved in closer to the flash flood to watch it, and then the second wave, twice as large and exponentially more powerful, came crashing down upon their location.

The realities of a "Godzilla" El Niño are already upon us, but unfortunately, the last time we experienced one was way back in 1997, meaning many people have already forgotten, and some were never there at all to begin with.

That year I chased a tropical cyclone up the Arizona/California border that maintained at Tropical Storm intensity well inland. Fortunately for many, most of its strong winds and heaviest rains ended up occurring over very sparsely populated areas of the desert. The next time such a rarity happens, larger communities may not be so lucky.

But as shown today in the tragedy along the Utah and Arizona borders, you do not need an intact tropical cyclone to create disastrous flooding in the desert southwest - which, unfortunately, has effectively been expanding over the past few years. Just the remnant moisture from El Niño & Blob fueled tropical depressions, storms and hurricanes can prove devastating.

The big takeaway, I think, is that residents and visitors to parts of the U.S. not typically accustomed to having to deal with the effects of severe tropical weather - Hawaii, California, Arizona, Nevada, Utah, and others - would be wise to learn about and prepare for the risks in their areas.

Sadly this week we've seen some examples of how this record-setting El Niño+Blob fueled weather is already impacting the southwestern United States, giving us some idea of how parts of the rest of the 2015 Pacific Hurricane Season, and indeed, likely a very tropically-connected winter and spring, could play out.

Quote:"I've lived here all my life, never seen anything like it... By the time we had the National Weather Service on the phone, it had already happened."

At least 16 deaths have now been confirmed in a flash flood tragedy this week near the Utah-Arizona border, including Zion National Park, in storms that were fueled by significant remnant moisture of former Hurricane Linda. (Still-updating story on KLS.com)

Additionally, today, September 15, 2015, the remnants of Category 3 Hurricane Linda conspired with an upper-level low off the California coast to deliver the most rain for any day in the month of September in Los Angeles since the September 1939 El Cordonazo~Lash of St. Francis Long Beach Tropical Storm, also making it the "second wettest September day on record at the downtown observation station where records date back to 1877," according to Weather.com

Past is prologue, and history does have a few examples of how El Niños can impact this part of the country, a part that is far more accustomed to seeing an Excessive Heat Warning, than warnings related to moisture or remnant circulations of tropical cyclones.

Here are a few of the more significant historical examples, sourced from Wikipedia:

Quote:

October 2, 1858: The 1858 San Diego hurricane was a very rare California hurricane. It is the only known tropical cyclone to impact California as a hurricane, although other systems impacted California as tropical storms. The storm caused damage to many homes and other constructions in San Diego. San Pedro experienced heavy rainfall, El Monte experienced high winds that damaged its corn crops and trees, and Los Angeles and Visalia experienced large amounts of rain but low wind. A later estimate stated that if a similar storm happened in 2004, it would have caused $500 million in damage.

September 4–7, 1939: The remnants of a hurricane brought over a year's worth of rain to parts of southern California

September 25, 1939: The 1939 California tropical storm, also called the 1939 Long Beach tropical storm, El Cordonazo, The Lash of St. Francis was a tropical cyclone that hit Southern California in September, 1939. Formerly a hurricane,[1] it was the only tropical storm to make landfall in California in the twentieth century... The flooding killed 45 in Southern California, although some of these may be attributable to the rain immediately before the tropical storm. At sea, 48 were killed.[1] The National Hurricane Center only attributes 45 deaths to this system.[7] Six people caught on beaches drowned during the storm. Most other deaths were at sea. Twenty-four died aboard a vessel called the Spray as it attempted to dock at Point Mugu. The two survivors, a man and a woman, swam ashore and then walked five miles (8 km) to Oxnard. Fifteen people from Ventura drowned aboard a fishing boat called the Lur. Many other vessels were sunk, capsized, or blown ashore.[6] Many low-lying areas were flooded. The Hamilton Bowl overflowed, flooding the Signal Hill area. Along the shore from Malibu to Huntington Beach houses were flooded. Throughout the area, thousands of people were stranded in their homes. Streets in Los Angeles proper were covered with water, flooding buildings and stalling cars. Flooding in Inglewood and Los Angeles reached a depth of 2 to 3 feet. Construction on a flood control project in the Los Angeles River's channel by the Army Corps of Engineers was stopped by the flooding. In Long Beach windows throughout that city were smashed by the wind. At Belmont Shore, waves undermined ten homes before washing them away. Debris was scattered throughout the coast. Agriculture was disrupted. Crop damage in the Coachella Valley reached 75%.

September 1970: Tropical Storm Norma was the fourteenth named tropical cyclone of the 1970 Pacific hurricane season. The storm formed off the coast of Mexico and intensified rapidly, peaking as a strong tropical storm on September 3 before starting a weakening trend which saw it dissipate before making landfall on Baja California. While the storm never made landfall, the remnants from the storm fueled the Labor Day Storm of 1970, which caused floods in Arizona that resulted in heavy damage and loss of life. The rainfall from this storm broke records, mostly for 24-hour rainfall totals. Despite not being tropical when the damages were done, Norma is considered to be the deadliest system in Arizona history.

September 10–11, 1976: Hurricane Kathleen was a tropical cyclone that caused destructive impacts in California. On September 7, 1976, a tropical depression formed; two days later it accelerated north towards the Baja California Peninsula. Kathleen brushed the Pacific coast of the peninsula as a hurricane on September 9 and made landfall as a fast-moving tropical storm the next day. With its circulation intact and still a tropical storm, Kathleen headed north into the United States and affected California and Arizona. Kathleen finally dissipated late on September 11... Damage in the United States was considerable. California received record rainfall, with over a foot of rain falling in some areas. Flooding caused catastrophic destruction to Ocotillo, and six people drowned. Flooding extended west; railway tracks were destroyed in Palm Desert and high winds and severe flooding were recorded in Arizona. Overall, the damage total was $160 million (1976 USD) and 12 deaths were attributed to the storm.

October 1983: Tropical Storm Octave was considered the worst tropical cyclone in the history of Arizona... In Arizona, the highest rainfall total was 12.0 in (300 mm) at Mount Graham. In Tucson, flood waters were reportedly 8 ft (2.4 m) high. Throughout the state, excessive rainfall caused many rivers to overflow. After the rain ended, the Santa Cruz, Rillito, and Gila rivers experienced their highest crests on record. Five towns – Clifton, Duncan, Winkelman, Hayden, and Marana – were almost completely flooded. In Marana, many homes were submerged, forcing residents to be evacuated. Over 700 homes were destroyed in Clifton. In addition, 86 of the town's 126 business were heavily damaged due to the flooding. Around 3,000 buildings were destroyed due to Octave. A total of 853 houses, mobile homes, and apartments were destroyed while 2,052 others were damaged. About 10,000 people were temporarily left homeless. Damage in Arizona totaled $500 million (1983 USD), which was above the preliminary estimate of $300 million. Fourteen people drowned and 975 persons were injured. Elsewhere, Octave was responsible for $12.5 million in damage in New Mexico.

September 25–26, 1997: Hurricane Nora was only the third tropical cyclone on record to reach Arizona as a tropical storm. Nora was the fourteenth named tropical cyclone and seventh hurricane of the 1997 Pacific hurricane season. The September storm formed off the Pacific coast of Mexico, and aided by waters warmed by El Niño, eventually peaked at Category 4... In the United States, there were no direct deaths blamed on the hurricane. However, the California Highway Patrol attributed three or four traffic fatalities in southern California to the weather.[15] Damage totals in the United States are not fully known, although media summaries of Nora included a loss to agriculture preliminarily estimated at several hundred million dollars, and at least one study places the figure at $150–200 million (1997 USD).[16] It is estimated that $30–40 million (1997 USD) in damage to lemon trees occurred.[17] Although Nora was significantly weakened, near hurricane-force winds were observed at the Dixie National Forest in southwestern Utah, where strong gusts sheared off the tops of large trees.

As of 3:30PM PST Sept. 19th, a core circulation center with associated deep convection that has been displaced to the west by moderate shear was centered near 21N 111.9W with an estimated minimum central pressure of 1003mb and maximum sustained winds of 30 MPH. Only a small increase in organization would trigger NHC advisories for this system, and a TCFA is now up.

This cyclone is of particular concern for residents of the southwestern United States and northwestern old Mexico, as it is heading nearly due north along a track that carries it across anomalously warm waters (nothing less than 24c up ahead should it follow an average of the models, and as high as 31c in the Gulf of California). On this track and given these waters, the cyclone could persist longer than usual, and possibly even intensify, bringing a potential of very heavy rainfalls and a risk of life-threatening flash floods to these parts of the US and Mexico.

97-C has been upgraded to TD 7-C, about 425 miles south of Hilo. It is expected to take a circuitous path north and NE and pass a couple hundred miles east of the Big Island in about 5 days, but there are a lot of moving parts out there creating a low confidence forecast. Recon will be heading to Hawaii to provide assistance.

We also have 98-C farther to the southwest that has a 100% chance of development and will probably become TD 8-C very soon. It is expected to track west into the Western Pacific. Also another disturbed area southeast of Hawaii (that does not have an invest tag as of yet - marked "Next Up" on the map above) that may develop and track north roughly behind 7-C over the next few days.

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